Nose-cone cooling of space vehicles



Y 23, 1966 J. E. LINDBERG, JR 3,267,356

NOSE-CONE COOLING OF SPACE VEHICLES Original FiledApril 5, 1962 2Sheets-Sheet 1 INVENTOR. JOHN E. L N08 ERG JR BY 6 Z ATTORNEY Aug. 23,1966 J. E LINDBERG, JR 3,267,35fi

NOSE-CONE COOLING OF SPACE VEHICLES 2 Sheets-Sheet 2 Original FiledApril 5, 1962 United States Patent 3,267,856 NOSE-CONE COOLING 0F SPACEVEHICLES John E. Lindberg, J12, 1211 Upper Happy Valley Road,

' Lafayette, Calif. Original application Apr. 5, 1962, Ser. No. 186,600.

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FIG. 2 is a greatly enlarged fragmentary view in elevation and insection of a portion of the shell of FIG. 1 showing incorporationtherein of one form of the present invention.

FIG. 3 is a further enlarged fragmentary view of a Divided and thisapplication Aug. 12, 1964, Ser. No. p of G. 2 showing one p oflaminatlon Struc- 389,103 ture suitable for use 111 the shell of FIG. 2.

1 Claim. (Cl. 10292.5) FIG. 4 is a fragmentary view in section takenalong the line 44 in FIG. 3.

This inventi n r la s t t HOSE-C0116 Coming of Space FIG. 5 is a view inelevation and in section of pertinent Vehifiles including missiles andmore Partioularly to portions of another missile, showing a differentshell strucsiles whose nose structures incorporate means fordissipatture embodying a difi d i f the invention, ing heat therfifrom-This application is adivis'ion of PP In order to illustrate theinvention more clearly, the cation Serial No. 186,600, filed April 5,1962, which is a figures have been made somewhat di i i formmlltimllation'in-part of application Serial 725,110, and do not show thecontents within the shell since the fil d Ma C 1958, HOW abandonedundesirable heat is developed at the shell and must be t i W611 knownthat an Object e'ntfiring the earths dissipated therefrom. The inventionis independent of atmosphere at even moderate speed is heatedconsiderably the contents f the hi l it lf by the attendant aerodynamicconditions at the surface AS an illustrative example f a Space hi l tohi h of the object. Such heating occurs when vehicles re-enter thisinvention applies, a missile 29 i Shown i F G 1 the atmosphere and is aSerious Problem, forcing drastic which indicates the general form of itsshell 30. Referlimitations on the maximum re-entry speed which astrucring next to FIG 2 it i be noted h h nose portion ture of givendesign can attain without being severely 31 f the shell 30 may belaminated to id layers 32 damaged or even destroyed. This heat isprimarily develand for example f a i bl heahconducting p and is largelyConcentrated at the nosemetal with alternate layers of heat-dissociablematerial 33 An important Object of the Present invention is To and 35sandwiched therebetween. The metal layers 32, eflici-ently dissipate theheat developed at the nose. By 34, and 36 are f bl between 0,005 and 0050" achieving this object, the invent-ion makes it possible to thick,while the layers 33 and 35 may be between about use higher re-entryspeeds and therefore gives greater Q0 and 0" thick Although only filayers 32 33 freedom in missile design and increases the missilesability 3 and 36 are Shown in the drawings, by Way f to avoidintelicelltionample, the laminated shell 30 in the nose region 31 typi-Another object of this invention is to provide a missile n has dozens fSuch laminations' structure wherein the heat developed at the nosesurface The heahdissociable material may be comprised f is carried toother parts of the missile and dissipated there, hydn'des f h 11 getter1 These d id thereby lowering the 11056 tempellatureas explained in mycopending application Serial No.

Other objects and advantages of the invention will ap- 695,357, filedNovember 8, 1957, now Patent No, 3,075,- P from the following detaileddescription of some P 361, are valuable heat-transfer agents, becausethe metalferred embodiments th r flic hydride is dissociated into metaland hydrogen in an In the drawings: endothermic reaction, absorbing alarge amount of heat FIG. 1 is a view in elevation and half in sectionof the 40 er unit Weight and per unit volume, as illustrated in shell ofthe forward portion of a missile. Tables I and II below.

TABLE I Thermodynamic properties of typical alkaline and alkaline earthhydrides Heat of dissociation in Heat of dissociation in Latent heat offusion of Latent heat of vapori- Specific heat of the metal Hydridegram-calories per gram gram-calories per cuthe metal in calories zationof the metal in in calories per cubic of compound bic centimeter ofcomper cubic centimeter calories per cubic cencentimeter per 0.

pound timeter near 20 0.

TABLE II Thermodynamic properties of typical Group B hydrides Heat ofdissociation in Heat 01 dissociation in Latent heat of fusion of Latentheat of vapori- Specific heat of the metal Hydride gram-calories pergram gram-calories per cuthe metal in calories zation of the metal in incalories per cubic of compound bic centimeter of comper cubic centimetercalories per cubic ccncentimeter per 0.

pound timeter near 20 C.

3 4 Certain metals such as copper, tungsten, iron, and 16,000 K. at oneatmosphere of pressure. Whether the nickel which form hydrides f theClass known as g p aforementioned properties are useful in a particularap- A (others are listed in my referred-to patent application Serial No.695,357) are suitable for use when combined with group B hydrides. Theformation of a group A hydride is endothermic, and, since thedissociation of a group plication, depends upon the actual temperatureof the 5 nose cone in that application. This temperature, in turn,depends upon the velocity of the vehicle and the medium B hydride isalso endothermic, the combination of a type m Whlch It IS i ThejseCondmons determme A metal with a group B hydride will absorb heat as thesome extent the optimum choice of heat transfer material temperature ofthe surrounding medium is elevated. and of engineering desigfl- Theexamples to b6 described Some. properties of type Ahydrides are listedin Table III. 10 will illustrate this. The gas temperature near the sur-TABLE III T hermodynwmic properties of typical hydrides of Group Amaterials Heat of formation in Heat of formation in Latent Heat offusion of latent heat of vaporiza- Specific heat of the metal Hydridegram-calories per gram gram-calories per the metal in calories tion ofthemetalin calin calories per cubic of compound cubic centimeter of percubic centimeter ones per cubic ceuticentimeter per C.

compound meter near C.

NlHQ 97. 2 684 641 12, 500 0. 93 CuH 79. 3 506 438 11, 200 0. 81

Suitable hydrides include the stoichiometric hydrides face of the nosecone may be found from the following of the alkali and alkaline earthmetals and the nonapproximate formula stoichiometric getter hydrides,some of which are listed above in Tables I and II, The stoichiometricmetallic 7) 2 hydrides are those of lithium, sodium, potassium rubidium,cesium, francium, calcium, strontium, barium, and radium, all of whichare suitable for this invention, except where: that some of them arecurrently expensive. Beryllium and magnesium form stoichiometrichydrides that decompose f Veloclty mlles P hour at low temperatures(beryllium hydride at about 125 C. T 0=m1t1a1 temperature of theatmosphere In a and magnesium hydride at about to T=temperature of thegas near the surface of the nose Suitable nonstoichi-ometric hydrides,members of group cone B arethose of scandium, titanium, vanadium,ytterbium, AS an example of the use of the formula zirconium, niobium,hafnium, tantalum, the rare-earth let: metals (atomic numbers 57-71),and the actinides (atomic numbers 8 940 3), though many of these arecurrently ex T 0 C. pensive and difficult to obtain in quantity.v=10,000 miles per hour Also useful are the borohydrides-compounds ofmetals 40 with the borohydride radical BH Examples are the thenborohydrides of aluminum, beryllium (decomposes at 10 000 2 123 C.),lithium (decomposes at 275 0.), sodium, zir- T =10,000 C. conium, etc.Of course, for most applications, some of 100 these are much more usefulthan others while still others are impractical in some situations. Theselection can be In the event i is q i that i l f may be tlaken of madeto accommodate the desired operating conditions. the heats ofdlssocfa'uon and of lomzatlon the hberated Alloys of hydrides are alsouseful, including alloys of It may be desirable to employ deut'mdesinstead of hydrides since the heats of dissociation and of ionizationfor deuterium are larger than those of hydrogen. For example, palladiumdeuteride, whose general properties correspond to thoseof palladiumhydride, may be used.

The first examples of my invention to be discussed are particularlyapplicable when the aerodynamic conditions at the nose cone producetemperatures below that required alkaline or alkaline earth hydridesalone, alloys of the nonstoichiometric hydrides, alloys comprised ofmembers of each group, and alloys of or with borohydrides therewith.Hereafter the generic term type B hydride shall be used to designate thealkaline earth and alkaline hydrides as well as the group Bnonstoichiometric getter hydrides, for appreciable ionization of a gas.These conditions In additions to the endothermic processes describedWill be experienced when a relatively small magnitude of previously asmeans of heat transfer, utilization may be heat is generated Over arelatively g Period of timemade of the latent heats of fusion andvaporization of the Under these conditions oxidation Of any 01' alloxidizable metals involved in the hydride and of a carrier for theunprottjcted surfaces of fluids released y take Place, hydride, Such asceramic or graphite. Fusion and vapor and oxidation is an undesirableexothermic reaction. ization are, of course, endothermic processes;fusion re- In the embodiment P I 1 and each layer 33, 35 quiring on theorder of a few hundred calories per cc. of (and f on) ofheat'dlssoclaple .material is connected to a metal and vaporizationrequiring about 5 to 15 kilocalories duct 38 (and so on) Whlch i extendsto and per cc. of metal. Similarly the heats of dissociation and ilaustsg; the aft end 39 of the mlsslle Shel; The metal of ionization of theliberated hydrogen may also, under i fi i &2)? 2 on) SID-W181 alloysteels or favorable conditions, be used for the heat transfer process.cogducgtoryand 32 2 f g w ch 18 also a good heat The magnitude of heatof dissociation of hydrogen is on y Goa e or Processed to prevent orretard oxidation. For example, the layers 32, 34, 36 may be siliconizedmolybdenum, i.e., molybdenum which has been processed to convert theskin to molybdenum disilicide to protect it from oxidation.

the order of 100 k.cal./mole H and that for the ionization is on theorder of 300 k.cal./mole hydrogen ions. In addition, when metallic vaporis present, it may also be possible to utilize its heat of dissociationand of ioniza- As heat is generated at the first metal laminatio 32 tionas valuable heat transfer mechanisms. Most gases I the first layer ofheat-dissociable material 33 receives mo t are fully dissociated above 8000 K. and are ionized above of the transferred heat. The result,particularly when a type B hydride is used, is an endothermic reactionwherein hydrogen is outgassed, removing a large quantity of heat as heatof dissociation (see Table II), and the hydrogen is then passed throughthe duct 37 and carried aft to the exhaust point 39, carrying with itsome of the developed heat contained in the hydrogen by virtue of itsrelatively high specific heat. At the exhaust point 39, the hydrogen mayoxidize and be used as desired or expelled. As the layer 33 becomesfully outgassed and can no longer transfer heat away from the metal 32by outgassing hydrogen in an endothermic reaction, the first thin layer32 of metal will melt away. The metal layer 32 may possibly oxidize butnot before heat transfer has been carried out by the endotherm of theheat dissociable reaction. This melting is also endothermic and willcool the nose 31 somewhat, exposing the first layer 33 of theheat-dissociable material. This layer 33, having outgassed, is nowsubstantially metal, and it too is carried away, as by melting, inanother endothermic reaction that tends to cool the nose 31. Table IVshows the melting points of typical metals.

The heat is now transferred chiefly by the next metal lamination 34 tothe next layer of heat-dissociable material 35, which outgasses throughits duct 38 to the end 39 of the missile. Since, as stated before, theremay typically be dozens of such layers, the process of heat transfer viathe heat of transformation of the heat-dissociable material, thetransportation of hydrogen, the melting of the metal layer, and themelting and dissipation of the outgassed metal, continues from layer tolayer always aiding in the cooling of the nose of the missile except forpossible oxidation, which, in any case, because of structural design,will be limited in its capacity to 0p pose the desired heat transfercharacteristics. The number, thickness, and composition of the metallayers and the heat-dissociable material layers may be adjusted bydesign to insure that all aerodynamic heating developed by the re-entryof the missile into the atmosphere will be dissipated before all theseprotective laminations have been destroyed. The heat dissociablematerials are so chosen that the dissociation endotherm is approximatelycompleted before temperatures are attained at which fusion of the metalsinvolved takes place.

At some given portion 40 (see FIG. 2) the layers are adjusted inthickness so that the nose 31 of the missile will always be a smoothcontour of proper shape as each layer is destroyed. Also, the ducts 37,38, etc., are so arranged that they are cleared of hydrogen upon thedissolution of the getter layers to which they are connected. The innerlayers of the getter material preferably terminate at progressivelygreater distances down the side of the nose cone, insuring that theoutgassed material will not burn too near to a duct that is thencarrying hydrogen from a lower outgassing layer. This is shown in thestepped construction of FIG. 2.

The laminations may be constructed as shown in FIGS. 3 and 4. Each layer33, 35, etc., of heat-dissociable material may be constructed by packinghydride 41 into cells 42 of sheets 41a of metal which have a honeycombform, such as Hexcell honeycombed metal. Other cells 41 are empty togive gas passages. The metal forming the honeycomb sheet 41a may be thesame as the metal in the layers 32, 34, and 36 or may be another metal,but in either case the metal should be one which has a melting pointabove the temperature required for completion of the dissociationendotherm of the heat-dissociable material. One side of each honeycombsheet 41a may then be intimately bonded to its outer layer 32, 34, etc.,while the unbonded side gives a gas passage 37, 38 between laminations.Structural members 40a which may be constructed of metal or ceramic areprovided to maintain the fabricated layers 33, 35, etc., rigidly inplace. They are small and do not obstruct gas flow through the passages37, 38. The laminations thus formed possess an advantage in that thereis more rapid transfer of heat through the metal 41a to the gettermaterial 41, and this rapid heat transfer increases the efiiciency ofthe nose cooling operation.

If desired, a relatively thick coating of ceramic or vitreous material43 may be applied over each layer of metal or over at least the outerlayer 32 to delay heating and thereby delay destruction of a given layerof the lamination. Such a coating 43 is preferably applied to the sideof the layer receiving the heat, and is illustrated in FIG. 2 where aceramic coat 43 is shown over the outer metal layer 32. There may becoatings over the layers 34 and 36 also, although these are notillustrated in this view.

A modified form of my invention employing endothermicallyheat-dissociable material for nose cooling of missiles is illustrated inFIG. 5. This structure is also useful for relatively small heatgeneration over a relatively long period of time. Here, a missile 44 hasa thin metal shell 45 which is separated from the inner body 46 by aduct 47. Typically, the shell 45 may be constructed of siliconizedmolybdenum or steel, as before. Toward the missiles nose 48 the duct 47may be filled with suitable heat-dissociable material 49 having a lowmelting point, such as lithium hydride, for example, which has beenfully ingassed. The remainder of the duct 47 may then be filledinitially with metal 50 native to the hydride 49. For example, iflithium hydride is used, the metal will be lithium.

Heat generated at the nose cone 48 of the missile is transferred throughthe metal shell 45, heating the hydride 49 adjacent thereto. If lithiumhydride is used, this hydride will become liquefied, because of its lowmelting point, and dissociated, each of these processes beingendothermic. Similarly the remaining lithium metal 50 in the duct 47will become liquefied. A pump 52 will pump the liquefied material in theduct 47 along pipes 53 to the nose 48 of the missile 44. This forces thedissociated lithium and hydrogen to a region 51 lying to the rear of thenose cone 48, where they recombine exothermically and release heat alongthe sides of the missile 44, where it is dissipated by radiation. Theliquid hydride thus formed is circulated by the pump 52 through thepipes 53 to the nose 48 of the missile for reuse. In this application itis necessary to choose hydrides which have low melting points or whichwill be in the liquefied state at temperatures below those for whichheat generation at the nose cone becomes a serious problem. This is soin order that the material may be continuously pumped by the pump 52.

In applying this method of nose cooling, some of the heat transferredfrom the nose 48 via the endothermic dissociation of the lithium hydridemay be utilized to gen erate power to drive the pump 52, instead ofdissipating this heat entirely. Thus, useful Work may be gained from thetransferred heat.

This method of nose-cone cooling possesses the advantage that theheat-transfer medium is not destroyed or exhausted from the missile butis reused in a cyclic process. Also, the heat generated at the nose 48may be transferred by the heat-transfer medium described to any locationdesired, for use in doing work or for dissipation, depending upon theintention of the designer of the missile. For example, the liquid metaland the hydrogen may be carried from the nose by separate ducts andallowed to recombine and liberate heat only over a relatively small areasuch as at the tail of the missile where the heat may be usedbeneficially. The recombination being an exothermic reaction, most ofthe heat will be carried as stored chemical energy and dissipated in therecombination reaction.

The nose shown in FIG. 5 may also be provided with an external ceramicor vitreous coating 54. This coating 54 serves to protect the metalshell 45 from oxidation in the region of greatest heating and alsoserves to delay heating of the missile.

To those skilled in the art to which this invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the spirit and scope of the invention. The disclosures and thedescription herein are purely illustrative and are not intended to be inany sense limiting.

I claim:

In a space vehicle, a nose having an imperforate outer surface andincorporating adjacent said surface a heatdissociable metallic hydridebelonging to the group of metals consisting of lithium, sodium,potassium, rubidium, cesium, francium, calcium, strontium, barium,radium, beryllium, magnesium, scandium, titanium, vanadium, ytterbiu-m,zirconium, niobium, palladium, hafnium, tantalum, the rare earth metals(atomic numbers 57-71), and the actinides (atomic numbers 89-103), saidhydride emitting hydrogen gas by dissociation when heated by atmosphericfriction against said nose, and means to convey the emitted gas awayfrom the nose upon dissociation of said hydride, said means to conveyincluding a pump for moving both the hydrogen and the metal back awayfrom the nose after after dissociation, means providing a coolingportion to which they are 'moved by said pump and where they recombineas a metallic hydride, and means for recirculating said cooled hydrideto said nose.

No references cited.

BENJAMIN A. BORCHELT, Primary Examiner.

F. C. MATTERN, JR., Assistant Examiner.

